4n

4N is a numeric designation that may refer to several distinct concepts in different fields. In metallurgy, materials science, and semiconductor manufacturing, 4N denotes a high purity level equal to four nines, or 99.99% purity. This grading is used for metals such as gold, copper, and nickel, as well as for silicon wafers and other semiconductor materials. Purity scales commonly use N, with 3N for 99.9%, 4N for 99.99%, and 5N for 99.999%.

In electronics and industrial parts, 4N appears as part numbers or family names of devices and components, such as 4N25, a widely used optocoupler, or as a prefix or series label in manufactured product lines. The use is not standardized, and the meaning of 4N in a given part number depends on the manufacturer's designation scheme.

In chess literature, Four Knights Game is a well-known opening that can sometimes be abbreviated informally as 4N in notes or diagrams, though this shorthand is not universal and should be interpreted from context.

Other uses include branding and model names where 4N is employed as part of a product code or designation across electronics, automotive, and consumer goods sectors. Because 4N is used in diverse ways, the precise meaning is context-dependent and should be inferred from accompanying information such as the subject or field.